What is magnetism?Magnetism is the properties and interactions ofmagnetsThe earliest magnets were found naturally in the mineralmagnetite which is abundant the rock-type lodestone.These magnets were used by the ancient peoples ascompasses to guide sailing vessels.Magnets produce magnetic forces and have magneticfield lines
Magnets have two ends or poles, called north andsouth poles. At the poles of a magnet, the magnetic fieldlines are closer together. Unlike poles of magnets attract each other and like poles of magnets repel.
The earth is like a giant magnet!The nickel iron core of the earth gives the earth amagnetic field much like a bar magnet.
What are magnetic domains?Magnetic substances like iron, cobalt, and nickel arecomposed of small areas where the groups of atoms arealigned like the poles of a magnet. These regions arecalled domains. All of the domains of a magneticsubstance tend to align themselves in the same directionwhen placed in a magnetic field. These domains aretypically composed of billions of atoms.
Electricity and Magnetism – howare they related?When an electric current passes through a wire amagnetic field is formed.
What is an electromagnet?When an electric current is passed through a coil of wirewrapped around a metal core, a very strong magneticfield is produced. This is called an electromagnet.
What is a galvanometer?A galvanometer is an electromagnet that interacts with a permanent magnet. The stronger the electric currentpassing through the electromagnet, the more is interactswith the permanent magnet.Galvanometers areused as gauges incars and many otherapplications.The greater the current passing through the wires, the strongerthe galvanometer interacts with the permanent magnet.
What are electric motors?An electric motor is a device which changes electricalenergy into mechanical energy.
How does an electric motor work?Go to the next slide
We have seen how electricity can produce a magneticfield, but a magnetic field can also produce electricity!How?What is electromagnetic induction?Moving a loop of wire through a magnetic field producesan electric current. This is electromagnetic induction.A generator is used to convertmechanical energy into electrical energy byelectromagnetic induction.Carefully study the next diagrams:
Direct current versus alternatingcurrent –AC vs DC : What’s the difference?Direct current is electrical current which comes from abattery which supplies a constant flow of electricity inone direction.Alternating current is electrical current which comesfrom a generator. As the electromagnet is rotated in thepermanent magnet the direction of the current alternatesonce for every revolution.
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